Some teleconferences are small and include, for example, 3-10 callers. Other teleconferences are larger and can include hundreds or even thousands of callers. Even when customers make advance reservations for a teleconference, the estimated number of callers is rarely accurate, sometimes being incorrect by a factor of 2 or more. It is therefore difficult to plan which resources to assign to a teleconference to ensure adequate capacity. If capacity is exceeded while a teleconference is in progress, callers for that teleconference are required to hang up and call again to connect to the teleconference using a different telephone number.